1. Field of the Invention
The invention relates to a device for improving the vacuum in an auxiliary device of a motor vehicle. The auxiliary device uses vacuum for various applications. Such an auxiliary device is often connected to the inlet manifold of a vehicle via a duct having a one-way valve directing the flow from the auxiliary device to the inlet manifold.
2. Background Information
Modern vehicles utilize vacuums formed in engine inlet manifolds for brake servo and other applications, such as central locking systems and climate control systems. However, at certain occasions the brake performance is low due to insufficient vacuum levels. The issue is accentuated, for example, during cold starts, at high altitudes and when driving on serpentine roads, alternately accelerating and braking. Fluctuating vacuum levels become more perceptible with additional auxiliary devices on the engine, automatic gearboxes, servo assisted steering, climate systems and exhaust emission systems. Variable valve timing and variable ignition timing can also make the vacuum variations more perceptible.
To increase the vacuum when, for example, starting a vehicle at high altitude having an automatic gearbox, a separate vacuum pump could be used. EP-A1-0549086 for example discloses a pump that has a housing, which has an upper and a lower flange between which is tightened a diaphragm, which is moved via a connecting rod and a shaft. The pump has an inlet and an outlet in which a control valve is arranged. A sealing ring is firmly connected to the lower flange of the pump and forms an apron with a cylindrical outer surface. A cover hood is set over the upper part of the pump, which has a cylindrical inner wall section fitting over the outer surface of the sealing ring, leaving a gap which is impenetrable to flame. The pump inlet and outlet are in flow connection via a seal with a suction connecting duct and a pressure-connecting duct through the covering hood.
Further, DE-A1-19853050 discloses a vacuum pump that has a working chamber for connection to a vacuum chamber of a vacuum braking pressure device amplifier and an outlet valve leading to ambient atmosphere. A membrane forming a boundary wall of the working chamber can be deflected in a working direction. An actuator coupled to the membrane contains an armature that can be moved in the working direction of the membrane by an electromagnetic coil.
The disadvantage with vacuum pumps in prior art is that they all require additional power, which at the above-mentioned conditions can be difficult.
A first non-limiting object of the present invention is to provide a device, which utilizes the pressure pulses in the inlet manifold of a vehicle to increase the vacuum in an auxiliary device, such as a brake servo/brake booster. A further object of the present invention is to provide a simple and non-expensive device for boosting vacuum levels for vehicle auxiliary devices.
Accordingly, the invention utilizes a chamber having an inlet and an outlet duct. The inlet duct is connected to a vacuum chamber of an auxiliary device. The chamber is separated from the inlet manifold with a flexible member. When the pressure in the inlet manifold decreases, the flexible member is drawn into the inlet manifold, thereby increasing the volume of the chamber. The pressure decreases in the chamber and a one-way valve arranged in the inlet duct opens and thus creating a flow from the vacuum chamber of the auxiliary device. Next the pressure in the inlet manifold increases and the flexible member of the device is pushed back into the chamber and the pressure increases in the chamber. At this point a valve in the outlet duct of the chamber opens and the system reaches equilibrium. This cycle is repeated and this increases the vacuum in the vacuum chamber of the auxiliary device.
Further advantages, objects and features of the invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying figures showing illustrative embodiments of the invention.